Sequential changes in the expression of genes involved in lipid metabolism in adipose tissue and liver in response to fasting

Abstract

The aim of this study was to provide a sequential analysis of the expression patterns of key genes involved in lipid metabolism in white adipose tissue (WAT) and liver and their relationship with blood parameters in response to fasting. Adult male rats were studied under different feeding conditions: feeding state, after 4, 8, or 24 h fasting, and after 3 h refeeding after 8 h fasting. Blood parameters and the expression of genes involved in lipogenesis and lipolysis in WAT and liver were analyzed. mRNA levels of genes involved in lipogenesis in liver (SREBP1c, FAS, and GPAT) had already decreased after 4 h fasting, as well as those of PPARgamma in WAT, whereas the decrease in SREBP1c, FAS, GPAT, and GLUT4 mRNA levels in WAT was observed after 8 h. Concerning lipolytic and fatty-acid-oxidation-related genes, liver PPARalpha, FGF21, CPT1, and PDK4 mRNA levels increased after 8 h fasting and those of ACOX1 after 24 h, and in WAT, ATGL, and CPT1 mRNA levels were greater after 24 h. Three hours refeeding increased the expression levels of PPARgamma in WAT, SREBP1c in both liver and WAT, and GPAT in liver, and decreased the expression levels of PPARalpha, CPT1, and PDK4 in liver. These results give new insight into the different adaptive time course response to fasting in the expression of genes involved in lipid metabolism, thus pointing out the very rapid response of lipogenic genes, particularly in liver, and the later response of lipolytic genes, particularly in WAT.

Impact of fasting time on hepatic lipid metabolism in nutritional animal studies

“…We also observed an increase in hepatic Pparα mRNA during fasting. The same observation has been reported in rats 8) and mice 19) fasted for 24 h. It has been suggested that an increase in hepatic Pparα mRNA during fasting is mediated by glucocorticoids. 20,21) PPARα may be activated by fatty acids liberated from adipose tissue.…”

“…8,14) However, these studies have only been done on 24-48 h of fasting, which can be a severe condition on small experimental animals such as rats and mice. Our results clearly showed that some Data are means ± SE of 6 rats.…”

“…Influence of more than 24 h fasting has also been investigated in some studies. 8,14) However, since 24 h fasting study on effects of functional food components is few, the 24 h fasting group was not included in the present study.…”

“…However, it is well known that fasting is an important factor in altering the enzyme activities and mRNA expression of genes related to energy and lipid metabolism. 8) Although there is a strong possibility that the influence of fasting on energy and lipid metabolism exceeds that of nutrients and food components, many researchers do not necessarily pay much attention to the effects of fasting on parameters related to lipid metabolism.…”

The Hepatic Genes for Immunoproteasome Are Upregulated by Refeeding after Fasting in the Rat

“…The process of energy management is regulated by hormones, and gene expression changes occur in peripheral tissues. Although information is available regarding the temporal gene expression changes that occur between feeding and fasting, [1][2][3][4] it is unclear how this shift arises. One reason for the lack of data is the difficulty in controlling the feeding behaviors of experimental animals.…”